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.\"
.\" Copyright 2012-2013 Samy Al Bahra.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"
.Dd April 20, 2013
.Dt CK_RING_DEQUEUE_SPMC 3
.Sh NAME
.Nm ck_ring_dequeue_spmc
.Nd dequeue pointer from bounded FIFO
.Sh LIBRARY
Concurrency Kit (libck, \-lck)
.Sh SYNOPSIS
.In ck_ring.h
.Ft bool
.Fn ck_ring_dequeue_spmc "ck_ring_t *ring" "ck_ring_buffer_t *buffer" "void *result"
.Sh DESCRIPTION
The
.Fn ck_ring_dequeue_spmc 3
function dequeues a pointer from the bounded buffer
pointed to by
.Fa ring
in FIFO fashion. The pointer is stored in the pointer
pointed to by
.Fa result .
The buffer pointed to by
.Fa buffer
must be unique to
.Fa ring .
The decoupling of the ring from the buffer serves
to address use-cases involving multiple address spaces
and DMA, among others.
If you are on non-POSIX platforms or wish for strict
compliance with C, then it is recommended to pass a
pointer of type void ** for
.Fa result .
This function is safe to call without locking for UINT_MAX
concurrent invocations of
.Fn ck_ring_dequeue_spmc 3
or
.Fn ck_ring_trydequeue_spmc 3
and up to one concurrent
.Fn ck_ring_enqueue_spmc 3
or
.Fn ck_ring_tryenqueue_spmc 3
invocation. This function provides lock-free progress
guarantees.
.Sh EXAMPLE
.Bd -literal -offset indent
#include <ck_ring.h>
/* This ring was previously initialized with ck_ring_init. */
ck_ring_t ring;
/* The ring was initialized for 1023 elements. */
ck_ring_buffer_t buffer[1024];
void
dequeue(void)
{
void *result;
/* Dequeue from ring until it is empty. */
while (ck_ring_dequeue_spmc(&ring, &buffer, &result) == true) {
/*
* Results contains the oldest pointer in ring
* since the dequeue operation returned true.
*/
operation(result);
}
/* An empty ring was encountered, leave. */
return;
}
.Ed
.Sh RETURN VALUES
The function returns true if the buffer was non-empty.
The result of the dequeue operation is stored in the
value pointed to by
.Fa result .
The function will return false if the buffer was empty
and the value in
.Fa result
will be undefined.
.Sh SEE ALSO
.Xr ck_ring_init 3 ,
.Xr ck_ring_trydequeue_spmc 3 ,
.Xr ck_ring_enqueue_spmc 3 ,
.Xr ck_ring_enqueue_spmc_size 3 ,
.Xr ck_ring_dequeue_spsc 3 ,
.Xr ck_ring_enqueue_spsc 3 ,
.Xr ck_ring_enqueue_spsc_size 3 ,
.Xr ck_ring_capacity 3 ,
.Xr ck_ring_size 3
.Pp
Additional information available at http://concurrencykit.org/
|
